1. Introduction
This document describes the modifications to OSPF to support version 6 of the Internet Protocol (IPv6). The fundamental mechanisms of OSPF (flooding, Designated Router (DR) election, area support, (Shortest Path First) SPF calculations, etc.) remain unchanged. However, some changes have been necessary, either due to changes in protocol semantics between IPv4 and IPv6, or simply to handle the increased address size of IPv6. These modifications will necessitate incrementing the protocol version from version 2 to version 3. OSPF for IPv6 is also referred to as OSPF version 3 (OSPFv3).
This document is organized as follows. Section 2 describes the differences between OSPF for IPv4 (OSPF version 2) and OSPF for IPv6 (OSPF version 3) in detail. Section 3 describes the difference between RFC 2740 and this document. Section 4 provides implementation details for the changes. Appendix A gives the OSPF for IPv6 packet and Link State Advertisement (LSA) formats. Appendix B lists the OSPF architectural constants. Appendix C describes configuration parameters.
1.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC-KEYWORDS].
1.2. Terminology
This document attempts to use terms from both the OSPF for IPv4 specification ([OSPFV2]) and the IPv6 protocol specifications ([IPV6]). This has produced a mixed result. Most of the terms used both by OSPF and IPv6 have roughly the same meaning (e.g., interfaces). However, there are a few conflicts. IPv6 uses "link" similarly to IPv4 OSPF's "subnet" or "network". In this case, we have chosen to use IPv6's "link" terminology. "Link" replaces OSPF's "subnet" and "network" in most places in this document, although OSPF's network-LSA remains unchanged (and possibly unfortunately, a new link-LSA has also been created).
The names of some of the OSPF LSAs have also changed. See Section 2.8 for details.
In the context of this document, an OSPF instance is a separate protocol instance complete with its own protocol data structures (e.g., areas, interfaces, neighbors), link-state database, protocol state machines, and protocol processing (e.g., SPF calculation).